Efficient Homes Weblog

I heard about a new house being built in a northern US city that was going to be fully passive solar. Check the glossary page for the difference between active solar and passive solar. This is a great approach to limiting energy consumption because it eliminates one of the largest energy consumers in the house and replaces it with the sun. What could be better?

In this case, there is a real problem. The house is a 2 story cape cod style, probably about 20′ tall. Immediately to the East-Southeast of this small property is a building that is 40+ ft tall. The new house won’t see any meaningful sunlight at all until 10:00 or 11:00am. Additionally, the long dimension of the building is oriented almost north-south, meaning that the smallest side of the house will be exposed to the sun.

With any solar heating system, the larger your solar collector is and the smaller your surface area of the building is, the better off you are. Ideally, the largest wall you have faces south and the rest of the walls are as small as you can make them.

My fear for this home owner is that their new house will be yet another good idea, implemented badly and will be too hot in the summer and will cause the home owner to do something inefficient, like add portable electric heaters, in the winter. In the end, I’m really skeptical that a passive solar house can be built on this lot at all. And, even if it is possible, it will require the design to be so driven by the passive solar aspect that there won’t be any flexibility left to, say, make the house not ugly, or allow some flexibility in how the house is used.

Houses last a long time, or at least they should, and will be used in different ways over time. Starter houses get used as small family houses that become large families, and maybe get sold to a retired couple. By trying to do the right thing in the wrong way, this house may be doomed by not being flexible enough to meet the needs of the people who live in it.

I can certainly see how an active solar house can be done here, and if there is a backup heat source that only gets used for a couple weeks a year, the home owners will be happier, the house will be renovated less, and the energy savings are much more likely to be realized.

Unfortunately, too many people see energy efficient design as a religion, rather than a technical discipline.